Quick, easy installation., Easily installs over the exhaust hole, under the eave (soffit) to exhaust air from bathroom fans., Helps prevent cold air from entering home, birds from nesting in vents and rodents from entering through vents,, Calcium filled Polypropylene, All components constructed of heavy duty plastic., Opening in soffit can be up to 5 diameter., For best installation practise use our EVEK4 kit to make a connection to the exhaust duct., UV Inhibitor added